阅读说明：本技术 片状物的缺陷检查用照明、片状物的缺陷检查装置和片状物的缺陷检查方法 (Illumination for inspecting defect of sheet, apparatus for inspecting defect of sheet, and method for inspecting defect of sheet ) 是由 杉原洋树 于 2019-08-23 设计创作，主要内容包括：本发明的特征在于,具有：对片状物照射照明光,且片状物的宽度方向为其长度方向的长尺寸的光照射机构；和第一遮光机构,其位于从光照射机构向片状物的光路间,在与光照射机构的长度方向平行的方向上交替排列有遮光部和开口部；和第二遮光机构,其在从所述光照射机构向片状物的光路间位于第一遮光机构与片状物之间,在与光照射机构的长度方向平行的方向上交替排列有遮光部和开口部,在第二遮光机构的遮光部与光照射机构之间具有第一遮光机构的开口部,第一遮光机构的开口部在与该光照射机构的长度方向平行的方向上的长度比第二遮光机构的遮光部在与该光照射机构的长度方向平行的方向上的长度短。(The present invention is characterized by comprising: a light irradiation mechanism for irradiating the sheet-like object with illumination light, wherein the width direction of the sheet-like object is the long dimension of the length direction; and a first light shielding mechanism which is positioned between the light paths from the light irradiation mechanism to the sheet-like object and has light shielding portions and openings alternately arranged in a direction parallel to the longitudinal direction of the light irradiation mechanism; and a second light shielding mechanism located between the first light shielding mechanism and the sheet-like object between an optical path from the light irradiation mechanism to the sheet-like object, the light shielding portions and the openings being alternately arranged in a direction parallel to a longitudinal direction of the light irradiation mechanism, the opening of the first light shielding mechanism being provided between the light shielding portion of the second light shielding mechanism and the light irradiation mechanism, a length of the opening of the first light shielding mechanism in the direction parallel to the longitudinal direction of the light irradiation mechanism being shorter than a length of the light shielding portion of the second light shielding mechanism in the direction parallel to the longitudinal direction of the light irradiation mechanism.)

1. An illumination for inspecting defects of a sheet, the illumination being used for inspecting defects of a sheet, the illumination comprising:

a long light irradiation mechanism that irradiates illumination light to a sheet-like object, the long light irradiation mechanism extending in a second direction orthogonal to a first direction in which the sheet-like object moves relative to the illumination on a surface of the sheet-like object; and

a first light shielding mechanism which is positioned between the light paths from the light irradiation mechanism to the sheet-like object and has light shielding portions and openings alternately arranged in a direction parallel to the second direction; and

a second light shielding mechanism located between the first light shielding mechanism and the sheet-like object at a position on an optical path from the light irradiation mechanism to the sheet-like object, the second light shielding mechanism having light shielding portions and openings alternately arranged in a direction parallel to the second direction,

an opening of the first light shielding mechanism is provided between the light shielding portion of the second light shielding mechanism and the light irradiation mechanism in a third direction orthogonal to the first direction and the second direction,

the length of the opening of the first light shielding mechanism in the second direction is shorter than the length of the light shielding portion of the second light shielding mechanism in the second direction.

2. The defect inspection illumination for a sheet according to claim 1, wherein the light shielding portion of the first light shielding mechanism and/or the light shielding portion of the second light shielding mechanism includes a light reflecting member protruding toward the light irradiation mechanism on a side facing the light irradiation mechanism.

3. A defect inspection device for a sheet material, comprising:

illumination for defect inspection of the sheet according to claim 1 or 2; and

an imaging unit that images light emitted from the defect inspection illumination and transmitted through the sheet-like object; and

and an image processing unit configured to detect a defect generated in the sheet based on the imaging data acquired by the imaging unit.

4. The defect inspection apparatus for a sheet according to claim 3, wherein a longitudinal direction of the light irradiation mechanism is parallel to a photographing direction of the photographing mechanism,

optical axes of the photographing mechanisms at respective positions in the photographing direction are parallel to each other,

at each position where the light emitted from the defect inspection illumination passes through the sheet, an angle formed by a transmission direction of the light passing through the sheet and an optical axis of the imaging mechanism is larger than an opening angle of the imaging mechanism.

5. A defect inspection device for a sheet material, comprising:

illumination for defect inspection of the sheet according to claim 1 or 2; and

an imaging mechanism that images light emitted from the defect inspection illumination and reflected by the sheet-like object; and

and an image processing unit configured to detect a defect generated in the sheet based on the imaging data acquired by the imaging unit.

6. The defect inspection apparatus for a sheet according to claim 5, wherein a longitudinal direction of the light irradiation mechanism is parallel to a photographing direction of the photographing mechanism,

optical axes of the photographing mechanisms at respective positions in the photographing direction are parallel to each other,

at each position where the light irradiated from the illumination for defect inspection is reflected by the sheet, an angle formed by a reflection direction of the light regularly reflected by the sheet and an optical axis of the imaging mechanism is larger than an opening angle of the imaging mechanism.

7. The apparatus for inspecting defects in a sheet according to claim 4 or 6, wherein the imaging means is provided with a telecentric lens.

8. The apparatus for inspecting defects in a sheet according to claim 4 or 6, wherein the imaging means includes a one-dimensional light receiving means having a length equal to a length in an imaging direction.

9. The apparatus for inspecting defects of sheet according to claim 8, wherein said one-dimensional light receiving mechanism is a contact image sensor.

10. A method for inspecting defects of a sheet by using an illumination means and an imaging means and imaging light emitted from the illumination means and transmitted through the sheet by the imaging means to inspect the presence or absence of defects in the sheet,

emitting, by the illumination mechanism, light in a second direction orthogonal to a first direction in which the sheet moves relative to the illumination mechanism on a surface of the sheet, the light having a transmission direction of the light transmitted from the sheet and an angle formed by an optical axis of the imaging mechanism at each position in which the light is transmitted from the sheet, the angle being larger than an opening angle of the imaging mechanism,

performing photographing by the photographing means in which a photographing direction is parallel to a second direction of the sheet and optical axes at respective positions in the photographing direction are parallel to each other,

and determining whether the sheet-like object has or does not have a defect using the image data captured by the imaging means.

11. A method for inspecting defects of a sheet by using an illumination means and an imaging means and imaging light emitted from the illumination means and reflected by the sheet by the imaging means to inspect the presence or absence of defects in the sheet,

with the illumination mechanism, light in which an angle formed by a reflection direction of the regular reflection light reflected by the sheet and an optical axis of the imaging mechanism at each position where the light is reflected by the sheet is larger than an opening angle of the imaging mechanism is emitted in a second direction orthogonal to a first direction in which the sheet moves relative to the illumination mechanism on a surface of the sheet,

performing photographing by the photographing means in which a photographing direction is parallel to a second direction of the sheet and optical axes at respective positions in the photographing direction are parallel to each other,

and determining whether the sheet-like object has or does not have a defect using the image data captured by the imaging means.

Technical Field

The invention relates to an illumination for inspecting defect of sheet, a defect inspection device of sheet, and a defect inspection method of sheet.

Background

Conventionally, in order to inspect the presence or absence of defects such as scratches on a sheet-like object having a smooth surface, there are the following inspection apparatuses and inspection methods: when a defect such as a scratch is present by irradiating light to the sheet, scattered light caused by the scratch is read to detect the defect such as the scratch on the sheet. In such an inspection apparatus, a linear light irradiation means such as a fluorescent lamp and an imaging means are generally disposed in a direction parallel or nearly parallel to the width direction of the sheet, and scattered light due to the defect is received and detected.

In general, the intensity of a defect (e.g., a scratch) is determined by the intensity of the received light amount (the magnitude of the light amount value) of the obtained scattered light, and the quality control is performed to prevent the product having a serious defect causing a quality problem from flowing out.

In the above-described method, defects such as scratches existing in a transparent sheet-like material are inspected, and there are cases where light is reflected by the sheet-like material and inspected, and cases where light is transmitted and inspected. The principle of detecting defects such as scratches on a continuously conveyed transparent sheet-like object by the above-described method will be described below with reference to fig. 13 to 16. Fig. 13 and 14 are explanatory diagrams of the principle of defect detection in the case of performing inspection by reflecting light off an inspection object, and fig. 15 and 16 are explanatory diagrams of the principle of defect detection in the case of performing inspection by transmitting light through an inspection object. In fig. 13 and 14, the linear irradiation light source 12 is disposed to extend in a direction perpendicular to the paper surface of the drawing, and similarly, the defect 100 (see fig. 14 and 16) on the sheet 5 also extends in a direction perpendicular to the paper surface. In general, since the width direction of the sheet 5 and the longitudinal direction of the linear irradiation light source 12 are often aligned, the sheet vertical direction (Y direction) is taken as the sheet width direction (light source longitudinal direction), the sheet horizontal direction (X direction) is taken as the sheet longitudinal direction and the conveying direction in which the sheet 5 is continuously conveyed (light source short side direction), and the sheet vertical direction (Z direction) is taken as the sheet vertical direction (imaging mechanism optical axis direction).

First, fig. 13 and 14 show: the linear irradiation light source 12 and the imaging mechanism 6 are disposed on the same surface side with respect to the sheet 5, and the defect is detected by detecting the reflected scattered light caused by the defect 100 existing on the surface of the sheet 5 in parallel with the width direction (Y direction). Here, the optical center line 8 of the imaging mechanism 6 is disposed to be shifted from an optical axis 10 (specular reflection optical axis) of light emitted from the linear irradiation light source 12 and specularly reflected by the sheet-like object. Therefore, in the case where the surface of the sheet 5 has no defect, as shown in fig. 13, the light is reflected only in a direction line-symmetric to the incident light with respect to the normal line (here, the Z direction) of the surface of the sheet 5, and the light does not enter the imaging mechanism 6. However, when the defect 100 parallel to the width direction (Y direction) exists on the surface of the sheet 5, as shown in fig. 14, the reflected and scattered light 14 is generated due to the defect 100 parallel to the width direction (Y direction). Of the reflected and scattered light 14, the component 15 directed to the imaging means 6 enters the imaging means 6, and the defect can be detected.

Next, fig. 15 and 16 show: the linear irradiation light source 12 and the imaging mechanism 6 are disposed with the sheet 5 interposed therebetween, and the defect is detected by detecting transmitted scattered light caused by the defect 100 existing on the surface of the sheet 5 in parallel with the width direction (Y direction). Here, the optical center line 8 of the imaging mechanism 6 is disposed offset from the optical axis of the linear irradiation light source 12. Therefore, when there is no defect on the surface of the sheet 5, the light is transmitted linearly without any scattering in the sheet as shown in fig. 15, and therefore the light is not incident on the imaging mechanism 6. However, when the defect 100 parallel to the width direction (Y direction) exists on the surface of the sheet 5, as shown in fig. 16, the transmission scattered light 16 is generated due to the defect 100 parallel to the width direction (Y direction). Of the transmitted scattered light 16, the component 17 directed to the imaging means 6 enters the imaging means 6, and the defect can be detected.

However, in the above method, when light having an incident surface perpendicular to the direction of the scratch is irradiated, the scattered light intensity is high and the sensitivity is high, whereas when light having an incident surface parallel to the direction of the scratch is irradiated, the scattered light is weak and the sensitivity is low. Therefore, in the above-described method, when a light source such as a fluorescent lamp or a parallel beam fiber lamp is used as a general linear irradiation light source, there is a problem that the detection sensitivity of the scratch parallel to the sheet width direction (Y direction) is high, and the detection sensitivity of the scratch parallel to the sheet length direction (X direction) is low.

Thus, patent document 1 discloses a technique for detecting a scratch parallel to the longitudinal direction (X direction) of a sheet with high sensitivity. Fig. 17 is a perspective view schematically showing the embodiment disclosed in patent document 1. As shown in fig. 17, patent document 1 discloses an inspection apparatus including a linear light irradiation mechanism 18 (including an optical fiber), an imaging mechanism 6, and the like. The imaging mechanism 6 is disclosed as a solid-state imaging device for detecting light, and performs reading by using a monitoring camera such as a line CCD camera. The linear light irradiation means 18 including an optical fiber is composed of at least 2-series optical fiber bundles 18a and 18b, and each series is arranged so that the optical axis direction of light emitted from the optical fiber emission end forms angles θ 7a and θ 7b with respect to the Z direction. In fig. 17, the light emission ends of the optical fiber bundles 18a and 18b face in different directions from each other. This inspection apparatus is a technique of irradiating light having an incident surface perpendicular to the defect 101 parallel to the longitudinal direction X of the sheet 5 to detect the defect. The angles θ 7a and θ 7b are constant in the X direction in any series, and such illumination is referred to as oblique illumination, and oblique illumination in which the angles θ 7a and θ 7b intersect is referred to as cross oblique illumination.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2008-216148

Disclosure of Invention

Problems to be solved by the invention

However, the inspection method of patent document 1 has the following problems. This problem will be described with reference to fig. 17. When the defect 101 parallel to the longitudinal direction (X direction) is detected, the inspection method of patent document 1 generates transmitted scattered light 16 having a certain degree of directivity and intensity distribution. The distribution and intensity of the transmitted and scattered light 16 depend on the intensity of the irradiation light 13, the angles θ 7a and θ 7b between the axis of the irradiation light 13 in the X direction and the Z direction, the intensity, shape, size, and the like of the scratch, but do not depend on the position of the scratch, and therefore, the transmitted and scattered light 16 generated by the defect 101 parallel to the longitudinal direction (X direction) becomes stronger when the scratch intensity is stronger and weaker when the scratch intensity is weaker. In general, the determination of the strength of a scratch in a detector depends on the amount of light received, but in the above case, a scratch having a low strength of a scratch cannot obtain a sufficient amount of light received, and a defect leak detection occurs.

To avoid such a missing inspection, in general, the angles θ 7a and θ 7b of the irradiation light 13 in the X direction with respect to the axis in the Z direction are reduced to such an angle that the incident light directly enters the imaging mechanism 6 without disturbing the inspection. This increases the intensity of the transmitted scattered light 16 generated by the scratch relatively to the intensity of the scratch, and can obtain a sufficient amount of received light to enable defect detection.

However, in the inspection method of patent document 1, an optical fiber is used as a means for controlling the angles θ 7a and θ 7b of the light irradiated from the linear light irradiation means 18. Since the optical fiber generally determines the opening angle of light (the spread angle of light from the exit end of the optical fiber) by its material, for example, the opening angle of light is 70 degrees in the case of a multi-component glass fiber which is generally used frequently, 60 degrees in the case of an inexpensive plastic fiber, and 25 degrees in the case of an expensive silica fiber. The distribution of light intensity in the light emission direction is strongest in the center direction perpendicular to the fiber ends, and the component spreading from this position in the peripheral direction is temporarily weakened. Therefore, since the opening angle of the optical fiber has a certain spread and the light intensity is inevitably reduced in the peripheral angle portion, there is a limit in detecting a scratch having a weak strength.

As described above, the light intensity distribution of the light emitted from the optical fiber in the light emission direction is strongest in the center direction perpendicular to the fiber end, and the component spreading from the center in the peripheral direction is temporarily weakened. However, although the component diffused in the peripheral direction is weak, a certain amount of light component leaks as diffused light from the light exit end surface, the side surface, and the like of the optical fiber. Therefore, if the linear light irradiation mechanism 18 including the optical fiber is provided directly below the optical axis center of the imaging mechanism 6, it is inevitable that the light component leaking from the optical fiber is directly incident on the imaging mechanism 6. Therefore, the light quantity is set to be sufficiently weak so that the brightness value of the leaked light component is saturated when imaging is performed by the imaging means 6 and detection of the scratch is not hindered. In this case, since the transmitted scattered light 16 generated by the scratch cannot be relatively intensified, a sufficient amount of received light cannot be obtained, and thus there is a limit in detecting the scratch having a weak strength.

Further, by setting the linear light irradiation mechanism 18 including the optical fiber in a state of being inclined from directly below the optical axis center of the imaging mechanism 6 in the sheet longitudinal direction (X direction), the light component leaking from the optical fiber is not directly incident on the imaging mechanism 6, and the luminance value is not saturated when the imaging mechanism 6 forms an image, and the light amount can be set to be high. However, in this configuration, the irradiation direction of light includes a combined direction of the longitudinal direction (X direction) and the width direction (Y direction), and light cannot be irradiated from a direction perpendicular to the defect 101 parallel to the longitudinal direction (X direction), and detection sensitivity of the defect 101 parallel to the longitudinal direction (X direction) cannot be sufficiently ensured.

For the above reasons, it is very useful to detect a scratch parallel to the longitudinal direction (X direction) of the sheet with high sensitivity.

The present invention has been made in view of the above, and provides a sheet defect inspection illumination, a sheet defect inspection apparatus, and a sheet defect inspection method, which detect scratches parallel to the sheet conveyance direction with high sensitivity.

Means for solving the problems

The defect inspection illumination for a sheet object according to the present invention for solving the above problems is an illumination for defect inspection of a sheet object, and includes:

a long light irradiation mechanism for irradiating the sheet-like object with illumination light, the long light irradiation mechanism extending along a second direction orthogonal to a first direction in which the sheet-like object moves relative to the illumination on the surface of the sheet-like object; and

a first light shielding mechanism which is positioned between the light paths from the light irradiation mechanism to the sheet-like object and has light shielding portions and openings alternately arranged in a direction parallel to the second direction; and

a second light shielding mechanism located between the first light shielding mechanism and the sheet-like object between the light paths from the light irradiation mechanism to the sheet-like object, the second light shielding mechanism having light shielding portions and opening portions alternately arranged in a direction parallel to the second direction,

an opening of the first light shielding mechanism is provided between the light shielding portion of the second light shielding mechanism and the light irradiation mechanism in a third direction orthogonal to the first direction and the second direction,

the length of the opening of the first light shielding mechanism in the second direction is shorter than the length of the light shielding portion of the second light shielding mechanism in the second direction.

In the defect inspection illumination for a sheet according to the present invention, it is preferable that the light shielding portion of the first light shielding means and/or the light shielding portion of the second light shielding means include a light reflecting member protruding toward the light irradiation means on a side facing the light irradiation means.

The defect inspection apparatus for a sheet material according to the present invention for solving the above problems includes:

the invention relates to a lighting for defect detection of sheet material; and

an imaging unit that images light emitted from the defect inspection illumination and transmitted through the sheet-like object; and

and an image processing unit configured to detect a defect occurring in the sheet based on the imaging data acquired by the imaging unit.

In the sheet defect inspection device according to the present invention, it is preferable that the longitudinal direction of the light irradiation means is parallel to the imaging direction of the imaging means,

the optical axes of the shooting mechanisms at the positions in the shooting direction are parallel to each other,

in each position where the light emitted from the defect inspection light passes through the sheet, an angle formed by a transmission direction of the light passing through the sheet and an optical axis of the imaging means is larger than an opening angle of the imaging means.

The defect inspection apparatus for a sheet material according to the present invention for solving the above problems includes:

the invention relates to a lighting for defect detection of sheet material; and

an imaging unit that images light emitted from the defect inspection illumination and reflected by the sheet-like object; and

and an image processing unit configured to detect a defect generated in the sheet based on the imaging data acquired by the imaging unit.

In the sheet defect inspection device according to the present invention, it is preferable that the longitudinal direction of the light irradiation means is parallel to the imaging direction of the imaging means,

the optical axes of the shooting mechanisms at the positions in the shooting direction are parallel to each other,

in each position where the light irradiated from the defect inspection illumination is reflected by the sheet, an angle formed by a reflection direction of the light regularly reflected by the sheet and an optical axis of the imaging mechanism is larger than an opening angle of the imaging mechanism.

In the defect inspection apparatus for a sheet-like object according to the present invention, the imaging means preferably includes a telecentric lens.

In the defect inspection apparatus for a sheet according to the present invention, it is preferable that the imaging means includes a one-dimensional light receiving means having a length equal to a length in an imaging direction.

In the defect inspection apparatus for a sheet according to the present invention, the one-dimensional light receiving means is preferably a contact image sensor.

The defect inspection method for a sheet object of the present invention for solving the above problems is a method for inspecting the presence or absence of defects in a sheet object by using an illumination means and an imaging means and imaging light emitted from the illumination means and transmitted through the sheet object by the imaging means,

with the illumination mechanism, light is emitted in a second direction orthogonal to a first direction in which the sheet moves relative to the illumination mechanism on a surface of the sheet, the second direction being a direction in which a transmission direction of light transmitted from the sheet at each position in which the light is transmitted from the sheet and an angle formed by an optical axis of the imaging mechanism is larger than an opening angle of the imaging mechanism,

the imaging means is configured to perform imaging by the imaging direction being parallel to the second direction of the sheet-like object and the optical axes at the respective positions in the imaging direction being parallel to each other,

and determining whether or not the sheet-like object has defects using the image data captured by the imaging means.

The defect inspection method for a sheet object of the present invention for solving the above problems is a method for inspecting the presence or absence of defects in a sheet object by using an illumination means and an imaging means and imaging light emitted from the illumination means and reflected by the sheet object by the imaging means,

with the illumination mechanism, light is emitted in a second direction orthogonal to a first direction in which the sheet-like object moves relative to the illumination mechanism on the surface of the sheet-like object, the angle between a reflection direction of the specular reflection light reflected by the sheet-like object and the optical axis of the imaging mechanism being larger than an opening angle of the imaging mechanism at each position where the light is reflected by the sheet-like object,

the imaging means is configured to perform imaging by the imaging direction being parallel to the second direction of the sheet-like object and the optical axes at the respective positions in the imaging direction being parallel to each other,

and determining whether or not the sheet-like object has defects using the image data captured by the imaging means.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to realize highly sensitive defect detection when detecting a scratch parallel to the sheet conveyance direction.

Drawings

Fig. 1 is a schematic view of an embodiment of a sheet defect inspection apparatus according to an embodiment of the present invention.

Fig. 2 is a schematic view of one embodiment of the defect inspection illumination for a sheet according to the embodiment of the present invention.

Fig. 3 is a schematic view of an imaging mechanism of modification 1, which is another embodiment of the defect inspection apparatus for a sheet material according to the present invention, and which is configured such that a telecentric lens is provided in a lens of the imaging mechanism.

Fig. 4 is a schematic view of an imaging mechanism of modification 2, which is another embodiment of the sheet defect inspection apparatus of the present invention, and which is a configuration in which a proximity image sensor is provided in the imaging mechanism.

Fig. 5 is a schematic view of a configuration in which a light reflecting member is provided in the first light shielding mechanism in the defect inspection illumination of the sheet of fig. 2 in the defect inspection illumination of modification 3.

Fig. 6 is a schematic view of a configuration in which a light reflecting member is provided in the second light shielding mechanism in the defect inspection illumination of the sheet of fig. 2 in the defect inspection illumination of modification 4.

Fig. 7 is a schematic view of another embodiment (modification 5) of the defect inspection illumination for a sheet material according to the present invention, in which a transparent plate-like body is provided between a first light shielding mechanism and a second light shielding mechanism.

Fig. 8 is a schematic view of a configuration in which a light reflecting member is provided in a first light shielding mechanism, according to an embodiment (modification 6) of the defect inspection illumination for a sheet of the present invention.

Fig. 9 is a schematic view of a configuration in which a light reflecting member is provided in the second light shielding mechanism, in one embodiment (modification 7) of the defect inspection illumination for a sheet of the present invention.

Fig. 10 is another embodiment (modification 8) of the defect inspection apparatus for a sheet material according to the present invention, and is a schematic view in which illumination and imaging means for defect inspection are arranged in a reflection configuration.

Fig. 11 is another embodiment (modification 9) of the defect inspection apparatus for a sheet material according to the present invention, and is a schematic view in which illumination and imaging means for defect inspection are arranged in a reflection configuration.

Fig. 12 is a schematic view of a configuration in which a linear irradiation light source is provided, according to another embodiment (modification 10) of the sheet defect inspection apparatus of the present invention.

Fig. 13 is an explanatory diagram of the principle of defect detection in the case where light is reflected by an object to be inspected to perform inspection.

Fig. 14 is an explanatory diagram of the principle of defect detection in the case of performing inspection by reflecting light on an object to be inspected.

Fig. 15 is an explanatory diagram of the principle of defect detection in the case of performing inspection by transmitting light through an inspection object.

Fig. 16 is an explanatory diagram of the principle of defect detection in the case of inspection by transmitting light through an inspection object.

Fig. 17 is a perspective view schematically showing the embodiment disclosed in patent document 1.

Detailed Description

Hereinafter, embodiments of illumination for inspecting a defect of a sheet, a defect inspection apparatus for a sheet, and a defect inspection method for a sheet will be described in detail with reference to the drawings. The present invention is not limited to the embodiment.

In the present invention, the "sheet-like material" refers to a sheet-like or plate-like material such as a film, but is not limited thereto. In the case of inspection using a transmission optical system, the inspection needs to be transparent or translucent. The "defect" means a scratch, a foreign substance, a stain, an unevenness, or the like existing on the surface or inside of the sheet-like object. The "imaging means" is a means capable of converting light into an electric signal, and is, for example, a line sensor camera in which light receiving elements are arranged one-dimensionally. However, not limited to the line sensor, an area sensor camera, a photomultiplier tube, or the like, which are two-dimensionally arranged, may be used. The "optical axis" refers to a line from the inspection surface toward the light receiving element of the imaging mechanism.

(embodiment mode)

< Defect inspection apparatus for sheet-like object >

The defect inspection apparatus for a sheet according to the embodiment of the present invention will be described in detail. The sheet defect inspection device of the present invention may be provided with the defect inspection illumination, the imaging means, and the image processing means of the sheet of the present invention, and the presence or absence of other means is not particularly limited. Therefore, other mechanisms described below are examples, and design changes can be made as appropriate.

The defect inspection apparatus for a sheet according to the present embodiment will be described with reference to fig. 1. Fig. 1 is a schematic view of an embodiment of a sheet defect inspection apparatus according to an embodiment of the present invention. Hereinafter, the conveyance direction in which the sheet 5 is continuously conveyed, the longitudinal direction (light source short side direction) of the sheet 5, the width direction of the sheet as the Y direction, and the vertical direction (imaging means optical axis direction) orthogonal to the longitudinal direction and the width direction as the Z direction are referred to. The X direction, the Y direction and the Z direction are orthogonal to each other. The width direction of the sheet is orthogonal to the longitudinal direction (conveying direction) of the sheet on the surface of the sheet. Fig. 1 (a) is a plan view showing the configuration of the defect inspection apparatus as viewed from the X direction. Fig. 1 (b) is a plan view showing the structure of the defect inspection apparatus viewed from the Y direction. The X direction corresponds to the 1 st direction, the Y direction corresponds to the 2 nd direction, and the Z direction corresponds to the 3 rd direction. The defect inspection apparatus is composed of a defect inspection illumination of the sheet of the present invention, an imaging means 6 for imaging light emitted from the defect inspection illumination and transmitted through the sheet 5, and an image processing means 7 for detecting defects generated in the sheet 5 based on imaging data acquired by the imaging means 6. The defect inspection apparatus is an example in which the defect inspection illumination and imaging means 6 is disposed in a transmissive configuration.

< illumination for inspecting defect of sheet >

Next, the defect inspection illumination for a sheet according to the present embodiment will be described with reference to fig. 1 and 2. Fig. 2 is a schematic view of one embodiment of the defect inspection illumination for a sheet according to the embodiment of the present invention. The light irradiation mechanism 1 irradiates the sheet 5 with light emitted from the light emitting unit 1 a. The light irradiation mechanism 1 is disposed such that the longitudinal direction thereof is parallel to the width direction (Y direction) of the sheet 5. The light emitting unit 1a is provided on one surface of the light irradiation means 1 facing the sheet-like object, and has a light emitting surface for emitting diffused light. The light irradiation mechanism 1 emits light along the width direction (Y direction) of the sheet 5. The light emitting section 1a is preferably configured by a fluorescent tube, LED lighting with a diffusion plate, or the like, because the diffused light is preferably completely diffused light. The light emitting section 1a may be configured by arranging a plurality of point-like light emitters such as LEDs and optical fibers uniformly. The emission color is not particularly specified, and white light having flat spectral wavelength characteristics, monochromatic light such as red, green, and blue, and light in a wavelength region other than visible light such as ultraviolet light and infrared light may be used, or light in any of these wavelength regions may be combined.

The first light shielding mechanism 2 is provided directly above the light emitting section 1 a. The first light shielding mechanism 2 includes a light shielding portion 2a and an opening portion 2 b. The light shielding portions 2a and the openings 2b are alternately arranged continuously in a direction parallel to the width direction (Y direction). The light shielding portion 2a of the first light shielding means 2 may be made of any material as long as it can shield the light irradiated from the light irradiation means. For example, a metal plate in which the light shielding portion 2a and the opening 2b are arranged continuously, which is manufactured by punching out a portion corresponding to the opening 2b of a strip-shaped metal plate, is suitably used. A resin plate may be used as long as the light-shielding property can be ensured. Further, the following configuration may be adopted: a strip-shaped plate having high transparency and no light-shielding property is used, and a light-shielding coating material is applied to a portion of the plate corresponding to the light-shielding portion 2a, or a light-shielding plate is bonded thereto. In either case, it is important to use a member capable of ensuring light-shielding properties in the light-shielding portion 2 a.

The second light shielding mechanism 3 is provided between the first light shielding mechanism 2 and the sheet 5. The second light shielding mechanism 3 also includes light shielding portions 3a and openings 3b in the same manner as the first light shielding mechanism 2, and the light shielding portions 3a and the openings 3b are alternately arranged continuously in a direction parallel to the width direction (Y direction). The light shielding portion 3a shields a part of the light transmitted through the opening 2b of the first light shielding mechanism 2, out of the light emitted from the light irradiation mechanism 1. The second light shielding mechanism 3 may have the same configuration as the first light shielding mechanism 2 as long as the light shielding portion 3a is formed of a member capable of ensuring light shielding performance.

Between the opening 3b of the second light shielding mechanism 3 and the light emitting portion 1a, the light shielding portion 2a of the first light shielding mechanism 2 is disposed so as to be aligned with the center position of the opening 3b in the vertical direction (Z direction). Further, between the light shielding portion 3a of the second light shielding mechanism 3 and the light emitting portion 1a, the opening 2b of the first light shielding mechanism 2 is arranged so as to be aligned with the center position of the light shielding portion 3a in the vertical direction (Z direction). Further, the length of the opening 2b of the first light shielding mechanism 2 in the width direction (Y direction) is shorter than the length of the light shielding portion 3a of the second light shielding mechanism 3 in the width direction (Y direction). With such a configuration, light transmitted through the opening 2b of the first light shielding mechanism 2 among light emission components in the vertical direction (Z direction) from the light irradiation mechanism 1 is shielded by the light shielding portion 3a of the second light shielding mechanism 3 and is not irradiated to the sheet 5. On the other hand, of the light components emitted from the light irradiation mechanism 1 and traveling obliquely in the width direction (Y direction) from the vertical direction, the light transmitted through the opening 2b of the first light shielding mechanism 2 and the opening 3b of the second light shielding mechanism 3 is irradiated to the sheet 5.

When the width of the light shielding portion 2a of the first light shielding mechanism 2 is a1, the width of the opening 2B of the first light shielding mechanism 2 is B1, the width of the light shielding portion 3a of the second light shielding mechanism 3 is a2, the width of the opening 3B of the second light shielding mechanism 3 is B2, the distance between the first light shielding mechanism 2 and the second light shielding mechanism 3 is H, the thickness of the first light shielding mechanism 2 is T1, and the thickness of the second light shielding mechanism 3 is T2, the minimum emission angle θ 1 and the maximum emission angle θ 2 of light emitted from the first light shielding mechanism 2 to the sheet 5 and transmitted through the 2 light shielding portions 2a and 3a can be obtained by the following expressions 1 and 2, respectively. The emission angle is an angle formed by light (traveling direction of light) and the optical axis direction (Z direction) of the imaging mechanism 6.

(formula 1)

θ1＝arctan((A2-B1)÷(2×H))

(formula 2)

θ2＝arctan((B2+(A2+B1)÷2)÷(H+T1+T2))

(imaging mechanism)

The imaging means 6 receives a component in the direction of the optical axis (optical center line 8) of the imaging means 6 among the light scattered, refracted, and reflected by the defect 100 on the sheet 5 from the light emitted from the defect inspection illumination toward the sheet 5, and outputs the received component as image data. On the other hand, when the sheet 5 has no defect 100, the imaging means 6 does not receive the component light in the direction of the optical center line 8. The imaging means 6 is preferably configured by using a combination of a line sensor camera having a one-dimensional light receiving means and an optical lens. When the imaging means 6 includes the one-dimensional light receiving means, the imaging means 6 is disposed such that the scanning direction of the imaging means 6 is parallel to the longitudinal direction (conveying direction) of the sheet 5. In addition, a combination of an area sensor camera having a two-dimensional light receiving mechanism and an optical lens may be used.

(image processing means)

The image processing means 7 receives the image data from the imaging means 6, and detects a defect (an image of the defect 100) if the image data contains the defect. The image processing means 7 may perform normal image processing for defect inspection. For example, the following means may be provided: a luminance unevenness correction means for performing luminance unevenness correction, a spatial filter for extracting only specific frequency component defect candidates from image data, a 2-valued means for screening the defect candidates by using luminance shading of the defect candidates, a determination means for determining whether or not the defect is a defect or the degree of the defect based on a combination of single or plural pieces of shape information such as an area and a length, and a period determination means for determining the periodicity of the defect occurring at a certain length period in the longitudinal direction X of the sheet 5; and so on. The discrimination result obtained by the image processing means 7 is reported or output to an external device by an output means provided in the image processing means 7. The determination result output to the external device is output by an output means provided in the external device or stored as determination information.

The defect inspection apparatus for a sheet material according to the present embodiment preferably includes: the longitudinal direction of the light irradiation mechanism 1 constituting the illumination for defect inspection is parallel to the imaging direction of the imaging mechanism 6, and the optical axes of the imaging mechanism 6 at respective positions in the imaging direction are parallel to each other. Thus, in the entire imaging range of the sheet 5, the angle formed by the optical axis of the imaging mechanism 6 and the light emitted from the defect inspection illumination (for example, light in the range of emission angles θ 1 to θ 2) is constant at any position in the imaging range. As a result, the defect can be detected with the same sensitivity regardless of the position in the imaging range. The "imaging direction" referred to herein is, for example, a scanning direction of a one-dimensional imaging element constituting a part of the one-dimensional light receiving mechanism, that is, an arrangement direction of the one-dimensional imaging element. In addition, it is preferable that: at each position where the light emitted from the defect inspection illumination is transmitted or reflected from the sheet 5, an angle formed by the transmission direction of the light transmitted from the sheet 5 or the regular reflection direction of the light reflected by the sheet 5 and the optical axis of the imaging mechanism 6 is larger than the opening angle of the imaging mechanism 6. Thus, when there is no defect in the sheet 5, the light emitted from the defect inspection illumination is not received by the imaging means 6, and therefore the inspection sensitivity is improved. The "opening (opening angle) of the imaging means" referred to herein is the maximum angle of an angle formed with respect to the optical axis of the imaging means 6 among the light that can be received by the imaging means 6. Light at an angle smaller than the opening (angle) of the imaging mechanism 6 is received by the imaging mechanism 6, but light at an angle larger than the opening (angle) is not received.

The defect inspection lighting provided in the defect inspection apparatus of the embodiment described above includes: a light irradiation means 1 for irradiating the sheet with illumination light, wherein the width direction of the sheet is the length of the sheet in the longitudinal direction; and a first light shielding mechanism 2 which is positioned between the light paths from the light irradiation mechanism 1 to the sheet-like object 5 and in which light shielding portions 2a and openings 2b are alternately arranged in a direction parallel to the longitudinal direction of the light irradiation mechanism 1; and a second light shielding mechanism 3 located between the first light shielding mechanism 2 and the sheet 5 between the light paths from the light irradiation mechanism 1 to the sheet 5, wherein light shielding portions 3a and openings 3b are alternately arranged in a direction parallel to the longitudinal direction of the light irradiation mechanism 1, wherein an opening 2b of the first light shielding mechanism 2 is provided between the light shielding portion 3a of the second light shielding mechanism 3 and the light irradiation mechanism 1, and wherein the length of the opening 2b of the first light shielding mechanism 2 in the direction parallel to the longitudinal direction of the light irradiation mechanism 1 is shorter than the length of the opening 3a of the second light shielding mechanism 3 in the direction parallel to the longitudinal direction of the light irradiation mechanism 1. According to the present embodiment, since the component in the optical axis (optical center line 8) direction of the imaging means 6 can be shielded from light and diffused light originating from a defect can be reliably detected, when scratches parallel to the longitudinal direction of the sheet-like object and the direction orthogonal to the longitudinal direction are detected, respectively, it is possible to perform highly sensitive defect detection.

The long sheet 5 may be conveyed in the longitudinal direction X by a roll-to-roll conveying process, or the sheet 5 in a single sheet state may be gripped and conveyed by a single-shaft or double-shaft linear conveying device. The sheet 5 may be fixed without moving or may be temporarily stopped, and the entire surface of the sheet 5 may be imaged by conveying the imaging mechanism 6 and the illumination for defect inspection while being held by a single-axis or double-axis linear conveying device. When the sheet 5, the imaging means 6, and the defect inspection illumination are conveyed, the conveying speed may be synchronized with the imaging timing of the imaging means 6 using a rotary encoder or a linear encoder.

(modification 1)

The imaging mechanism 6 may include a telecentric lens as an optical lens. The details will be described with reference to fig. 3. Fig. 3 is a schematic view of an imaging mechanism of modification 1, which is one embodiment of the defect inspection apparatus for a sheet material according to the present invention, and which is configured such that a telecentric lens is provided in a lens of the imaging mechanism. Since the telecentric lens 6a is a lens having an aperture stop at the focal point of the lens, unlike a normal optical lens, the principal rays are parallel to the object side (the sheet 5 side), the image side (the imaging mechanism side), or both sides of the lens with respect to the optical axis of the lens (the angle of view is 0 degrees). Therefore, the optical axis of the imaging mechanism 6 is oriented in a constant direction within the effective field of view of the telecentric lens 6 a. It is thus possible to easily realize: at each position where the light emitted from the defect inspection illumination for the sheet is transmitted or reflected from the sheet 5, the angle formed by the direction of the light transmitted or reflected from the sheet 5 and the optical axis of the imaging means 6 is made larger than the opening angle of the imaging means 6.

(modification 2)

The imaging means may include a one-dimensional light receiving means having a length equal to the length of the imaging region (length in the imaging direction) in the width direction (Y direction) of the sheet 5. More specifically, the one-dimensional light receiving mechanism may also use a contact image sensor. The details will be described with reference to fig. 4. Fig. 4 is a schematic diagram of an imaging mechanism according to modification 2, in which a proximity image sensor is provided in the imaging mechanism. The proximity Image Sensor 11 is also called a Contact Image Sensor or a CIS (Contact Image Sensor), and has a one-dimensional light receiving Sensor array 11a having the same width as a field of view of imaging and a rod lens array 11b of an equal magnification imaging system lens provided on a front surface thereof. An optical system configured by combining a normal optical lens and a camera has a reduction or enlargement magnification depending on the size relationship between the imaging field of view and the image sensor, and therefore, a field angle is generated in the optical system according to the magnification, whereas the field angle is parallel (0 degrees) because the proximity image sensor 11 is an equi-magnification optical system. Therefore, the optical axis of the imaging mechanism 6 is substantially constant within the effective field of view of the proximity image sensor 11.

According to modification 2, the length in the imaging direction is made to coincide with the width of the one-dimensional light receiving means, so that: at each position where the light irradiated from the defect inspection illumination for the sheet is transmitted or reflected from the sheet 5, the angle formed by the direction of the light transmitted or reflected from the sheet 5 and the optical axis of the imaging mechanism 6 is made larger than the opening angle of the imaging mechanism 6.

(modification 3)

The defect inspection illumination for a sheet of the present invention may have a configuration other than that shown in fig. 2. Refer to fig. 5. Fig. 5 is a schematic view of a configuration in which a light reflecting member 2c is provided in the first light shielding mechanism 2 in the defect inspection illumination of the sheet material of fig. 2 in the defect inspection illumination of modification 3. A light reflection member 2c capable of reflecting and scattering light from the light emitting portion 1a is provided on the light irradiation mechanism 1 side of the light shielding portion 2a of the first light shielding mechanism 2. The light reflecting member 2c is in a shape protruding toward the light irradiation mechanism 1 side. According to the present modification 3, the light emitting component that is blocked by the light blocking portion 2a of the first light blocking mechanism 2 and is not irradiated to the sheet 5 is reflected and scattered by the light reflecting member 2c to change the optical path, and thus can be transmitted through the opening 2b and the opening 3b and irradiated to the sheet 5. Thus, the light irradiated to the sheet 5 via the light reflecting member 2c becomes light in an angular range from the minimum emission angle θ 3 to the maximum emission angle θ 4. The light reflecting member 2c is preferably in a left-right symmetrical triangular shape because it is preferable to irradiate light with the same amount of light and inclination in the left-right direction as the width direction Y, but may be in a shape corresponding to a desired emission angle range.

(modification 4)

Refer to fig. 6. Fig. 6 is a schematic view of a configuration in which a light reflecting member 3c is provided in the second light shielding mechanism 3 in the defect inspection illumination of the sheet of fig. 2 according to modification 4. A light reflecting member 3c capable of reflecting and scattering light transmitted through the opening 2b of the first light shielding mechanism 2 is provided on the light irradiation mechanism 1 side of the light shielding portion 3a of the second light shielding mechanism 3. The light emitting component that has passed through the opening 2b of the first light shielding mechanism 2 but has been shielded by the light shielding portion 3a of the second light shielding mechanism 3 and has not been irradiated to the sheet 5 is reflected and scattered by the light reflecting member 3c to change the optical path, so that the light emitting component can be transmitted through the opening 3b and irradiated to the sheet 5. Thus, the light irradiated to the sheet 5 via the light reflecting member 3c becomes light in an angular range from the minimum emission angle θ 5 to the maximum emission angle θ 6. The light reflection member 3c is preferably a right-left symmetrical triangular shape, as in the light reflection member 2c, since it is preferable that the light reflection member irradiates light with the same amount of light and inclination in the right-left direction as the width direction Y.

According to the present modifications 3 and 4, by providing the light reflecting member 2c or the light reflecting member 3c, a part of the light emission component which is emitted from the light irradiation means 1 and is shielded by the light shielding portion 2a or the light shielding portion 2b without being irradiated to the sheet 5 in the embodiment can be irradiated to the sheet 5, and therefore, the light use efficiency is improved.

(modification 5)

Refer to fig. 7. Fig. 7 is a schematic view of another embodiment (modification 5) of the defect inspection illumination for a sheet material according to the present invention, in which a transparent plate-like body 4 is provided between a first light shielding mechanism 2 and a second light shielding mechanism 3. As the transparent plate-like body, a glass plate, a transparent resin plate, or the like is suitably used. According to the present modification 5, the refractive index of light is higher than that in the case where the first light shielding mechanism 2 and the second light shielding mechanism 3 are interposed with air, and therefore the distance H between the first light shielding mechanism 2 and the second light shielding mechanism 3 can be shortened accordingly (see fig. 2).

(modification 6)

Fig. 8 is a schematic view of a configuration in which a transparent plate-like body 4 is provided between a first light shielding mechanism 2 and a second light shielding mechanism 3, and a light reflecting member 2c is provided in the first light shielding mechanism, according to an embodiment (modification 6) of the defect inspection illumination for a sheet material of the present invention. A light reflection member 2c capable of reflecting and scattering light from the light emitting portion 1a is provided on the light irradiation mechanism 1 side of the light shielding portion 2a of the first light shielding mechanism 2. The light reflection member 2c and the plate-like body 4 in the embodiment of fig. 8 have the same effects, materials, and shapes as the light reflection member 2c in the embodiment of fig. 5 and the plate-like body 4 in the embodiment of fig. 7.

(modification 7)

Fig. 9 is a schematic view of a configuration in which a transparent plate-like body 4 is provided between a first light shielding mechanism 2 and a second light shielding mechanism 3, and a light reflecting member 3c is provided in the second light shielding mechanism, according to an embodiment (modification 7) of the defect inspection illumination for a sheet material of the present invention. A light reflecting member 3c capable of reflecting and scattering light transmitted through the opening 2b of the first light shielding mechanism 2 is provided on the first light shielding mechanism 2 side of the light shielding portion 3a of the second light shielding mechanism 3. The light reflection member 3c and the plate-like body 4 in the embodiment of fig. 9 have the same effects, materials, and shapes as the light reflection member 3c in the embodiment of fig. 6 and the plate-like body 4 in the embodiment of fig. 7.

The configuration in which the light reflecting member 2c is provided in the light shielding portion 2a of the first light shielding mechanism 2, the configuration in which the light reflecting member 3c is provided in the light shielding portion 3a of the second light shielding mechanism 3, and the configuration in which the transparent plate-like body 4 is provided between the first light shielding mechanism 2 and the second light shielding mechanism 3 may be each independently or in combination of a plurality of them.

(modification 8)

Refer to fig. 10. Fig. 10 is another embodiment (modification 8) of the sheet defect inspection apparatus of the present invention, and is a schematic view of the arrangement of the defect inspection illumination and imaging means 6 in a reflective configuration. Fig. 10 (a) is a plan view showing the configuration of the defect inspection apparatus viewed from the X direction. Fig. 10 (b) is a plan view showing the structure of the defect inspection apparatus viewed from the Y direction. In fig. 10, the light irradiation mechanism 1 emits light parallel to the X direction, and a part of the light passes through the first light shielding mechanism 2 and the second light shielding mechanism 3 and enters the beam splitter 9. Further, the light passing through the beam splitter 9 from the sheet 5 enters the imaging mechanism 6. The beam splitter 9 bends light incident from the X direction toward the Z direction (here, the sheet 5 side) and passes light incident from the Z direction. In this defect inspection apparatus, light emitted from the defect inspection illumination is bent by a beam splitter 9 disposed on an optical center line 8 of the imaging means and is irradiated to the sheet 5, and light reflected by the sheet 5 is received by the imaging means 6 through the beam splitter 9.

(modification 9)

Refer to fig. 11. Fig. 11 is another embodiment (modification 9) of the sheet defect inspection apparatus of the present invention, and is a schematic view of the arrangement of the defect inspection illumination and imaging means 6 in a reflective configuration. Fig. 11 (a) is a plan view showing the configuration of the defect inspection apparatus viewed from the X direction. Fig. 11 (b) is a plan view showing the structure of the defect inspection apparatus viewed from the Y direction. The defect inspection illumination is disposed at an angle such that the optical axis thereof is inclined from the vertical direction (Z direction) with respect to the surface of the sheet 5. The imaging mechanism 6 is disposed at a position where light emitted from the defect inspection illumination is regularly reflected by the sheet 5 and the reflected light is received.

(modification 10)

Refer to fig. 12. Fig. 12 is another embodiment (modification 10) of the defect inspection apparatus for a sheet material according to the present invention, and is a schematic view of a configuration in which a linear irradiation light source 12 is further provided in addition to the defect inspection illumination for a sheet material according to the present invention. Fig. 12 (a) is a plan view showing the configuration of the defect inspection apparatus as viewed from the X direction. Fig. 12 (b) is a plan view showing the structure of the defect inspection apparatus viewed from the Y direction. In modification 10, the configuration of the above embodiment further includes a linear irradiation light source 12. The linear irradiation light source 12 may be disposed parallel to the light irradiation mechanism 1, and may irradiate light at a position where the sheet 5 is irradiated with the defect inspection illumination for the film-like object. The linear irradiation light source 12 may be disposed on either the upstream side or the downstream side with respect to the conveyance direction of the sheet 5, or on both sides. The linear irradiation light source 12 may be disposed at a light transmission position with respect to the imaging mechanism 6 through the sheet 5, or may be disposed at a position where light irradiated to the sheet 5 is reflected. By providing the linear irradiation light source 12, for example, inspection sensitivity of the defect 100 in the width direction Y of the sheet can be achieved.

Industrial applicability

The present invention is not limited to the inspection of defects existing on sheet-like or plate-like objects, and can be applied to the inspection of defects such as fine irregularities and foreign matter, and the application range is not limited thereto.

Description of the reference numerals

1 light irradiation mechanism

1a light emitting part

2 first light-shielding mechanism

2a light-shielding part

2b opening part

2c light reflecting member

3 second light-shielding mechanism

3a light-shielding part

3b opening part

3c light reflecting member

4 transparent plate-like body

5 sheet-like article

6 shooting mechanism

6a telecentric lens

7 image processing mechanism

8 optical center line of shooting mechanism

9 beam splitter

10 positive reflection optical axis

11 short-range image sensor

11a one-dimensional light receiving sensor array

11b rod lens array

12 line-shaped irradiation light source

13 irradiating light

14 reflected scattered light

15 component of the reflected and scattered light directed to the imaging means

16 transmission scattered light

17 a component of the transmitted scattered light toward the imaging means

18 linear light irradiation mechanism including optical fiber

18a, 18b fiber optic bundles

100 defect

101 defect parallel to the longitudinal direction Y

θ 1 minimum exit angle of light transmitted from 2 light shielding mechanisms

Theta 2 maximum emission angle of light transmitted from the 2 light shielding mechanisms

θ 3 minimum emission angle of light transmitted through the reflection part existing in the light shielding part of the first light shielding mechanism

θ 4 maximum emission angle of light transmitted through the reflection part existing in the light shielding part of the first light shielding mechanism

θ 5 minimum emission angle of light transmitted through the reflection part existing in the light shielding part of the second light shielding mechanism

θ 6 maximum emission angle of light transmitted through the reflection part existing in the light shielding part of the second light shielding mechanism

Angle of optical axis of light emitted from optical fiber bundle of theta 7a and theta 7b

Opening angle of light emitted from optical fiber